A cap made of synthetic resin material is often fitted on an opening of a container for foods, drugs and cosmetics. The cap often consists of a primary cap having an outlet opening at a top wall thereof, and a secondary cap adapted to close this outlet opening.
For instance, Japanese utility model publication (kokai) No. 1-66355 discloses a container cap including a primary cap 1 and a secondary cap 2 which are joined together by a pair of flexible hinge strips 3a having a reduced thickness, and also by a resilient piece 3b so that the direction of the biasing force of the resilient piece may be reversed from the closing direction to the opening direction and vice versa depending on the angular position of the secondary cap. This utility model publication also discloses a plate member 4 which is slidably guided on a top surface of the primary cap and provided with a tapered surface 5, and allows the secondary cap to be opened up with a single hand by pushing the plate member which in turn pushes up the secondary cap with its tapered surface and pushes the inner surface of the resilient piece 3b with a free end 6 thereof.
However, according to this prior art, the thinned hinge portions show on the exterior in two places, and the resilient piece protrudes outward when the secondary cap is opened. These facts are highly detrimental to the external appearance. This conventional cap provides the advantage of allowing the secondary cap to be opened up with a single hand but involves a large number of fabricating and assembling work steps and a complex management of the component parts because a slidable member is made of a separate member, and needs to be molded separately and assembled to the primary cap.